The present invention relates generally to semiconductor lasers, and more specifically to coupled resonator vertical-cavity lasers having multiple lasing wavelengths.
A very useful component in a wide variety of laser and optical applications would be a compact, efficient, low-power laser able to emit laser radiation at a number of distinct wavelengths. The ability to switch from one lasing wavelength to another, triggered by an electrical and/or optical signal has one set of uses, while the ability to simultaneously lase at multiple wavelengths has another.
The ability to switch from one lasing wavelength to another has potential uses in optical switching, optical interconnection, wavelength-domain optical data transmission, spectroscopy, and other applications. Simultaneous lasing at multiple wavelengths appears to have special usefulness in spectroscopic applications, but also can have uses in many of the same areas for which switchable lasing wavelengths are useful.
There is therefore a long-felt need for a small, efficient, low power laser device which is capable of lasing at multiple wavelengths, either simultaneously, or which is capable of switching between the different lasing wavelengths.
Vertical-cavity surface emitting lasers (VCSELs) are small in size, and operate with reasonable efficiency and at quite low power. They are thus a reasonable candidate as the basis for a multiple wavelength laser which is small enough to enable the above applications, and also have the advantage that large numbers of VCSELs can be integrated into a single integrated circuit.
Conventional vertical-cavity surface emitting lasers (VCSELs) generally comprise a slab of active laser gain medium sandwiched between a pair of dielectric mirrors, these substructures being monolithically integrated on the surface of a semiconductor substrate. Such devices are usually lattice-matched or strained-layer structures, made of single-crystal direct-gap semiconductor materials. The most common materials used for construction are gallium arsenide based semiconductor alloys. VCSELs are commonly used to optically transfer information from one subsystem to another, either via free-space coupling or by coupling to a fiber optic.
A class of coupled-resonator vertical-cavity laser devices which are capable of lasing at multiple wavelengths has been invented. These lasers comprise vertically stacked multiple regions of electrically-pumped laser gain media, each such region being located in optically coupled resonators. Each region of laser gain media can be independently injected with current, resulting in an operating parameter space with distinct regions of optical behavior. These device""s can be switched between different lasing wavelengths, or can be made capable of simultaneously lasing at multiple wavelengths.